How Does the Heart Work?

This is the first post in a 3 part series. Part 2 (How Does Your Heart Know to Contract), Part 3 (What Causes the Most Common Heart Problems?)

Your heart is literally vital to your well being. If your heart stops beating effectively no other part of your body can survive. This is because oxygen and nutrients will no longer be moving around in your body.

Your heart is a large muscle that has 4 hollow spots inside. These are called chambers. While your heart is one large muscle, we discuss it in terms of having a “left side” and a “right side.” This is because all four heart chambers don’t directly connect to each other. The left and right sides of your heart are separated by heart muscle. There are 2 chambers on your right side and two chamber on your left side. The two chambers are set so that one is above the other and they are separated by a doorway called a valve.

A Red Blood Cell’s Journey Through the Heart

Blood is in constant motion in your body. For the sake of simplicity we are going to talk through the heart from the perspective of a red blood cell. This red blood cell is just returning to the heart from your veins. It is ready to get rid of the carbon dioxide it is carrying and pick up fresh oxygen. Also for the sake of simplicity when I mention the hearts contraction I am speaking in terms of the bottom chambers of your heart (the ventricles) contracting.

Our red blood cell arrives back to the heart from your largest vein. It enters into the first chamber of your heart, called the Right Atria. As your heart relaxes, the valve that separates your Right Atria and the next chamber of your heart, the Right Ventricle (located directly below your Right Atria) opens. The open valve allows our red blood cell to flow directly down into the Right Ventricle. During the next contraction of the heart, this valve will close. By closing this keeps blood moving in the correct direction through the heart. Otherwise, our red blood cell could get pushed back up into the Right Atria again.

As our first valve closes, a new valve opens. This valve separates the Right ventricle from the large blood vessel that connects to the lungs. This open valve allows the blood carrying our red blood cell to be pushed out of the heart so that it can travel to the lungs. During our red blood cells trip to the lungs it hands over the carbon dioxide waste that it is carrying so that it can be exhaled by our lungs. It then has it’s roughly 270 million hemoglobin proteins each pick up 4 new molecules of oxygen to take back out to your body’s cells. Before it can get back out to your body though, our red blood cell has to travel back to your heart.

This time as your heart contracts, the large vessel carrying your blood away from the lungs dumps our red blood cell into the Left Atria of the heart. As the heart relaxes, the valve separating the Left Atria from the Left Ventricle (located directly below your left atria) opens. This allows our red blood cell to enter the Left Ventricle. During the heart’s next contraction, the the valve that our red blood cell just went through closes. Again, this ensures that our red blood cell continues to travel in the right direction. We want it to go out to the body to deliver oxygen, we don’t want it to get pushed back up to the left atria.

As that valve closes, a new valve opens. This valve separates the Left Ventricle from the large artery called your Aorta. This valve opens as your heart contracts and allows the blood to go out to the rest of the body. Our red blood cell is now on it’s way to deliver oxygen to our body’s cells!

As the blood leaves your heart there are several different arteries that it will get divided into. One artery path sends blood to your arms and legs and the organs beyond your heart. One artery path is your Carotid Arteries and they bring blood and nutrients to your head and brain. Another artery path provides blood to the heart muscle itself. These are your Coronary Arteries and are extremely important. Because if your heart muscle doesn’t receive oxygen and nutrients it will no longer be able to contract. And as we discussed earlier, if your heart muscle is not able to contract effectively then no other part of your body can survive.

“Now I’m Going to listen to Your Heart”

Have you ever wondered what exactly your health care team is listening for when they put their stethoscope on your chest? They are listening for a sound like a “lub-dub” and this is made by the valves of your heart opening and closing. You have probably noticed that they listen to your heart in multiple spots. Depending on where their stethoscope is located they are listening to a different valve. As we learned above your heart has 4 different valves. As your heart relaxes, the two valves between your Atria and your Ventricles open while the valves between your Ventricles and the large blood vessels leaving the heart close. Then when your heart contracts, the valves separating your Atria and your Ventricles close and the valves separating your Ventricles and the large blood vessels open allowing blood to travel out of your heart. The “lub, dub” sound is each valve opening and closing. If a valve is not functioning properly your healthcare team may be able to hear different sounds such as blood flowing back through a valve that is supposed to be closed.